Machine for washing fibrous suspensions

ABSTRACT

A machine for washing fibrous suspensions has a pair of cylindrical drums; and a flexible belt with through holes carried by the drums. A conveyor carries the suspension to a contact line between the flexible belt and the first drum. A drive rotates at least one of the drums; and a collection received and pollutant agents; and another collection recess of the cellulose fibres. The conveyer has a head box below the flexible belt and upstream the first drum. The head box has a conveying conduit and) an outlet mouth transversally disposed with respect to the flexible belt. A flow conveyor, disposed between the head box and the first drum, has a laminar body with an inlet edge, downstream the outlet mouth, and an outlet edge, immediately upstream the contact line of the flexible belt with the first drum.

BACKGROUND OF THE INVENTION

The present invention is about a machine for washing the cellulose fibre which is used in paper manufacture.

It is known that, in paper manufacturing processes, different stocks of cellulose fibre are used, whose characteristics should be carefully selected since they are determinant for defining the quality of the manufactured paper.

In particular, the cellulose fibre has to be separated from the pollutant particles present therein, which are particularly relevant when the feedstock is for instance waste paper.

Such separation is obtained with the aid of particular machines for washing fibrous suspensions which, although in their different specific embodiments, all substantially consist of a pair of drums, of which at least a driven one, around which a flexible belt provided with through holes is wound as a loop ring.

The pair of drums comprises a grooved drum, provided with a plurality of mutually parallel circumferential grooves, and a smooth drum, provided with a scraper under which a container for collecting the washed cellulose fibre is disposed.

In the first stage of the washing operation, the cellulose fibre is dispersed, together with the pollutant substances, in a solution based on water contained inside a container.

The container communicates with a head box whose outlet mouth is disposed beneath the flexible belt, parallel to the drums axis, and it is turned toward the area in which the flexible belt begins to wind on the grooved drum.

The fibrous suspension which exits from the outlet mouth of the head box penetrates, between the belt and the grooved drum, remaining adherent therein and turning together with said drum in the winding portion of the flexible belt.

During this stage the suspension, due to the centrifugal force induced by the rotation of the drum, releases water and the impurities, normally of smaller size with respect to the cellulose fibres, which pass in the through holes of the flexible belt and are collected on the outside.

In such way, the fibrous suspension is set free from water and from the impurities contained therein under the effect of the centrifugal force induced by the rotation around the drum, which drives the water in the through holes of the flexible belt.

Subsequently, the cellulose fibre which remains adherent to the inner part of the flexible belt is conveyed to the second smooth drum, where it undergoes a compression between the cylinder surface and the belt surface, allowing the elimination by squeezing of a further quantity of water.

Once the squeezing is finished, when the belt leaves the smooth drum, the cellulose fibre depurated by the pollutant substances and the water remains adherent to the drum, from which it is detached by means of a scraper put in contact with its surface.

The detached fibre is collected by gravity inside an underneath container, from which it is then extracted by means of an auger that conveys it to the subsequent utilizations.

The cited known machines for washing fibrous suspensions have some acknowledged inconveniences.

A first inconvenience is due to the fact that, in the zone upstream the winding point of the belt around the drum, even many of the shortest cellulose fibres pass through the holes of the flexible belt together with the fluid and the impurities contained in the suspension, thus being dispersed.

Such inconvenience occurs because of the difference between the speed of the suspension conveyed through the head box outlet mouth and the speed of the belt.

Said speed difference generates the grazing of the fibre mass against the surface of the belt and causes priming of turbulent movements which cause the passage of the shortest fibres, together with the impurities, through the belt holes.

It is evident that such loss of fibre involves a loss of feedstock, with a consequent costs increase.

Another acknowledged inconvenience is due to the fact that, always because of the turbulent movement to which the fibrous suspension penetrating between the flexible belt and the drum is submitted, the shortest cellulose fibres tend to pass through the belt holes even in the zone immediately downstream the contact line between the belt and the drum, with further losses of feedstock.

A further inconvenience is due to the fact that, in the machines of known type, it is not possible to modify the characteristics of speed and thickness of the fluid flow outgoing from the head box, unless the pressure above the head box, and thus the throughput, is changed.

Not the least inconvenience is also due to the fact that the washing machines of known type produce a considerable quantity of water polluted by the impurities extracted by the washed suspension, which have to be properly treated in depurators before being eventually reused in the productive cycle.

The present invention intends to eliminate the aforementioned inconveniences.

SUMMARY OF THE INVENTION

It is a first object of the invention to provide for a machine for washing the cellulose fibre which allows to reduce the quantity of shortest cellulose fibres that are eliminated, together with the impurities, passing in the through holes of the flexible belt during the washing process.

It is another object of the invention to provide for a machine for washing the cellulose fibre which allows to modify the characteristics of speed and thickness of the fluid film of cellulose fibres, being equal the throughput of the fluid to be treated.

Not the least object of the invention is to provide for a machine for washing the cellulose fibre which allows to reduce the quantity of water to be purified, polluted by the impurities extracted by the suspension.

Said objects are obtained by providing for a machine for washing fibrous suspensions composed by cellulose fibres and pollutant agents dispersed in a liquid which, according to the main claim, comprises:

-   -   a frame;     -   at least a pair of cylindrical drums with substantially parallel         and mutually spaced axes;     -   a flexible belt provided with through holes and wound as a loop         ring on said pair of cylindrical drums;     -   conveying means able to carry said fibrous suspension at the         zone of incipient contact between said flexible belt and a first         drum of said at least a pair of drums;     -   driving means able to put in rotation at least one of said drums         to move forward said flexible belt;     -   collecting means of said liquid and said pollutant agents which         are filtered through said flexible belt by the centrifugal force         impressed to said fibrous suspension by the rotation of said         first drum;     -   collecting means of said cellulose fibres contained in said         fibrous suspension which are transferred from said flexible belt         on the lateral surface of a second drum of said at least pair of         drums,         and wherein said conveying means comprise:     -   a head box disposed below said flexible belt and above said         first drum, said head box comprising a conveying conduit of said         fibrous suspension provided with an outlet mouth transversally         disposed with respect to said flexible belt for at least a         portion of its width;     -   a flow conveyor disposed between said head box and said first         drum, said flow conveyor comprising a laminar body in which an         inlet edge, disposed downstream said outlet mouth of said head         box, and an outlet edge, disposed immediately upstream the         contact line of said flexible belt with said first drum, are         provided.

Advantageously, the presence of a conveyor disposed between the head box and the contact line between the belt and the drum allows the fibrous suspension to undergo a gradual acceleration, avoiding that a turbulent movement, typical of the known embodiments, is created therein, which generates the discharge of the shortest cellulose fibres through the belt holes, together with the impurities.

In such way, a first squeezing of the suspension between the belt and the conveyor is favoured, with the displacement on the surface of the longest fibres which block the dispersion of the shortest ones through the belt holes.

Still advantageously, the presence of the conveyor allows the suspension to be conveyed between the drum and the belt without the turbulent movements which, in the cited known embodiments, determine the loss of the shortest cellulose fibres through the belt holes.

In fact, the suspension to be treated arrives in the contact zone with the drums with the same speed of the belt and thus, being null the suspension-belt relative speed, no mutual grazing is generated.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforesaid objects and advantages will be better highlighted in the description of preferred embodiments of the invention, given in an explanatory and not limiting way, with reference to the figures of the annexed drawings, wherein:

FIG. 1 is a side view of the machine of the invention;

FIGS. 2 and 3 show two details of the machine of FIG. 1;

FIGS. 4 and 5 show two details of the drum of the machine of FIG. 1;

FIG. 6 shows a detail of the flow conveyor of the machine of FIG. 1; and

FIG. 7 shows another executive embodiment of the machine of FIG. 1.

DESCRIPTION OF THE INVENTION

The machine of the invention is shown in FIGS. 1 and 2, where it is generally indicated with numeral 1, and it is adapted for washing fibrous suspensions S composed by cellulose fibres and pollutant agents dispersed in a liquid.

It comprises a frame 2 which supports a pair of cylindrical drums 3, 4 with substantially parallel and mutually spaced axes, between which a flexible belt 5 provided with through holes 6 is wound as a loop ring.

Conveying means 7 carry the fibrous suspension S to be washed at the zone 8 of incipient contact between the flexible belt 5 and the first drum 3 of the pair of drums 3, 4.

Concerning the pair of drums 3, 4, the first drum 3 has a plurality of circumferential grooves 3 a, while the second drum 4 has a smooth surface 4 a.

Driving means 9, comprising a first pulley 17 keyed to the motor 18, a second pulley 19 keyed to the grooved drum 3 and a transmission belt 20 wound between the aforementioned pulleys 17, 19, put in rotation the first drum 3 to move forward the flexible belt 5 in the direction indicated by the arrow 21.

It is intended that, in another embodiment, the driving means could be also of other kind and they could be differently connected to one or even both drums.

The cellulose fibres contained in the fibrous suspension S are transferred from the flexible belt 5 on the lateral surface 4 a of a second drum 4, which is part of the pair of drums 3, 4 equipping the washing machine 1, at which collecting means 11 of said fibres are present.

As one can see, said collecting means 11 comprise a scraper 24 put in contact with the lateral surface 4 a of the drum 4 and a container 25 for collecting the detached fibres, placed under the scraper 24.

The container 25 for collecting the washed cellulose fibre is internally provided with extraction means, which preferably but not necessarily consist of an auger 26 for conveying said fibre to the subsequent utilizations.

On the lower part of both drums 3, 4 means 10 are present, for collecting the liquid and the pollutant agents which, filtered through the flexible belt 5 during the washing process, then fall by gravity on the collecting means 10.

According to the invention, the conveying means 7 comprise:

-   -   a head box 12 disposed below said flexible belt 5 and above said         first drum 3, said head box 12 comprising a conveying conduit 13         of said fibrous suspension S, provided with an outlet mouth 14         transversally disposed with respect to said flexible belt 5 for         at least a portion of its width;     -   a flow conveyor 15 disposed between said head box 12 and said         first drum 3, said flow conveyor 15 comprising a laminar body 16         in which an inlet edge 16 a, disposed downstream said outlet         mouth 14 of said head box 12, and an outlet edge 16 b, disposed         immediately upstream the contact line of said flexible belt 5         with said first drum 3, are provided.

As one can see in FIG. 6, the flow conveyor 15 comprises a laminar body 16 which has a shaped surface, turned toward the flexible belt 5, in which, starting from the inlet edge 16 a disposed downstream the outlet mouth 14 of the head box 12, a bent portion 16 c with the convexity turned toward the flexible belt 5 is present, followed by a straight portion 16 d which ends with an outlet edge 16 b disposed at the point 8 of incipient contact between the grooved drum 3 and the flexible belt 5.

The straight portion 16 d of the laminar body 16 is substantially parallel disposed with respect to the flexible belt 5.

Concerning the outlet mouth 14 of the head box 12, it is provided with opening adjustment means 26 which consist of a sliding blade 27 disposed on the width of the conveying conduit 13 and provided on one side with screw means 28 to fix the head box 12 to the conveying conduit 13.

The laminar body 16 is joined to the sliding blade 27 of the above described conveying conduit 14, so that the displacement of the latter generates the sliding of the laminar body 16 in order to maintain its inlet edge 16 a always at the same distance from the outlet mouth 14 of the conveying conduit 13.

In particular, the sliding blade 27 surface turned toward the opposite side of the flexible belt 5 is inclined with respect to the belt 5 at an angle β having double amplitude with respect to the inclination angle γ of the corresponding surface of the laminar body 16, it too being turned toward the opposite side of the flexible belt 5.

The laminar body 16 surface turned toward the opposite side of the flexible belt 5 abuts, at its intermediate point 31, against a support structure 32 fixed to the conveying means 7.

Said surface is shaped so that its sliding on the support structure 32, because of the opening adjustment of the outlet mouth 14 of the conveying conduit 13, takes place according to a trajectory which allows the surface turned toward the flexible belt 5 to remain constantly parallel to said belt.

Concerning the screw means 28 to fix the sliding blade 27 to the conveying conduit 13, they comprise a plurality of screws 33, each of them being provided with a control wheel 34, passing through the slot obtained in the sliding blade 27 and being screwed in a corresponding threaded hole obtained in the conveying conduit 13.

The flow conveyor 15 is furthermore provided with side shoulders 35, applied to the laminar body 16, able to laterally contain the fibrous suspension S which slides on its surface.

As shown in FIGS. 1 and 2, the machine 1 further comprises thrust elastic means 36 put in contact with the outer surface of the flexible belt 5, on the opposite side with respect to the laminar body 16, able to generate a slight pressure on the belt 5 to allow an initial squeezing of the fibrous suspension S against the surface of the laminar body 16.

However, in other executive embodiments, the machine could be provided with a single collecting container in which either the liquid coming from the first drum or that coming from the second drum is indifferently conveyed.

Operatively, the flexible belt 5 moves forward in the counterclockwise direction shown by the arrow 21, being put in motion by friction by the grooved drum 3 and being wound on the second drum 4 which, on the contrary, is idle and it is supported by a central shaft.

The fibrous suspension S exits from the head box 12 through the conveying conduit 13, it is guided by the first bent portion 16 c of the laminar body 16 and, after being passed through the straight portion 16 d of the laminar body 16, where it undergoes an acceleration that makes it to have the same advancement speed of the flexible belt 5, it enters in contact between the drum 3 and the flexible belt 5.

In such way, thanks to the gradual contact of the suspension S with the flexible belt 5, the grazing and the start of turbulent movements, whose effect is to disperse the shortest cellulose fibres in the through holes 6 of the belt 5, are avoided.

The presence of the elastic means 36 promotes already in this stage a first slight squeezing of the fibrous suspension S, which allows the longest fibres to reach the surface near the belt 5, generating a grid that avoid the shortest fibres to pass outwardly through the holes 6 obtained in the flexible belt 5 and thus being dispersed.

The fibrous suspension S penetrates between the grooved surface 3 a of the first drum 3 and the flexible belt 5, passing through the portion wound on the grooved drum 3 of said belt; in this way, the fibrous suspension S, being disposed inside the grooves 3 a obtained on the drum 3, undergoes a centrifugation action which allows to eliminate water and the pollutant substances contained therein.

The liquid composed by water and pollutant substances, which is eliminated by centrifugal effect through the holes 6 of the flexible belt 5, is collected in a first tank 22 placed below the grooved drum 3 and it is sent therefrom to the outside of the machine 1.

The washed cellulose fibre remains adherent to the inner surface of the lower run 5 a of the flexible belt 5, which conveys it in contact with the lateral surface 4 a of the second drum 4, where it undergoes a further loss of water by the compression between the surface 4 a of the second drum 4 and the flexible belt 5.

In a similar way with respect to the preceding one, the water discharged through the holes 6 of the flexible belt 5 is collected in a second tank 23 and sent therefrom to the outside of the machine 1.

The presence of two distinct collecting tanks 22, 23 allow the liquid coming from the first drum 3, containing a considerable quantity of pollutant agents, not to be mixed with the liquid coming from the second drum 4, where the squeezing of the fibrous suspension S takes place.

In fact, while the liquid contained in the first collecting tank 22 has to be depurated, the liquid contained in the second collecting tank 23 can be directly used, since the very low quantity of pollutant substances contained therein, in other processes of the paper mill.

The cellulose fibre then reaches the upper part of the second drum 4, where it is put in contact with the scraper 24 which detaches it from the surface 4 a of the drum 4 to make it fall by gravity inside the collecting means 11, from where the auger 26 provides for laterally sending it away from the machine 1.

Acting on the adjustment means 26 of the outlet mouth 14 opening, it is possible to control, being equal the throughput, the speed and the thickness of the fibrous suspension S conveyed to the first drum 3 through the flow conveyor 15.

The adjustment means 26, consisting of the previously described sliding blade 27, are joined to the laminar body so that the displacement of the blade 27 is followed by a sliding of the laminar body 16 on the support structure 32, in order that the surface of the laminar body 16 is maintained always parallel to the surface of the belt 5, to warrant a correct sliding of the fibrous suspension S.

In the executive embodiment shown in FIG. 7, generally indicated with numeral 100, the first cylindrical drum 37 is disposed at a higher level with respect to the second drum 39, so that the upper and lower rectilinear portions of the flexible belt 40 are inclined.

Such configuration allows to reduce the water quantity that is ejected upwardly under the effect of the centrifugal force, in the direction indicated by the arrow 41, thus avoiding that it can soak again the just squeezed fibres conveyed in the collecting tank 42.

Furthermore, the positioning of the first drum 37 at a higher level with respect to the previously described embodiment 1 allows to increase the capacity of the water and pollutant substances collecting tank 43, avoiding that the head 44 is put in contact with the drum 37.

In fact, the water coming from the first drum 37 by the effect of the centrifugation of the fibrous suspension S represents about the 80% of the water contained in the suspension S.

On the basis of the aforesaid description, it should be understood that the machine of the invention, in all the described embodiments, achieves all the intended objects.

In particular, it is achieved the object to provide for a machine for washing a cellulose fibre which allows to reduce the quantity of shortest cellulose fibres that are eliminated, together with the impurities, passing in the through holes of the flexible belt during the washing process, and this is obtained using the flow conveyor.

It is achieved the object to provide for a machine for washing a cellulose fibre which allows to modify the characteristics of speed and thickness of the cellulose fibres fluid film, being equal the flow of fluid to be treated, and this is obtained through the adjustment means, which modifies the opening of the head box outlet mouth.

It is achieved the object to provide for a machine for washing a cellulose fibre which allows to reduce the quantity of discharged water to depurate, polluted by the impurities extracted by the suspension, and this is obtained using the two collecting tanks, which allow to separate the more polluted water coming from the first drum from that, containing less impurities, coming from the second drum.

Modifications and variations to the machine 1 of the invention, not described and not shown in the drawings, could be introduced in the executive stage.

All the described and any other not cited embodiments, if they fall within the scope of protection of the following claims, should be intended as protected by the present patent. 

1. A machine for washing fibrous suspensions composed by cellulose fibres and pollutant agents dispersed in a liquid, comprising: a frame; at least a pair of cylindrical drums with substantially parallel and mutually spaced axes; a flexible belt provided with through holes and wound as a loop ring on said pair of cylindrical drums; conveying means able to carry said fibrous suspension at the zone of incipient contact between said flexible belt and a first drum of said at least a pair of drums; driving means able to put in rotation at least one of said drums to move forward said flexible belt; collecting means of said liquid and said pollutant agents which are filtered through said flexible belt by the centrifugal force impressed to said fibrous suspension by the rotation of said first drum; collecting means of said cellulose fibres contained in said fibrous suspension which are transferred from said flexible belt on the lateral surface of a second drum of said at least pair of drums, wherein said conveying means comprise: a head box disposed below said flexible belt and above said first drum, said head box comprising a conveying conduit of said fibrous suspension provided with an outlet mouth transversally disposed with respect to said flexible belt for at least a portion of its width; a flow conveyor disposed between said head box and said first drum, said flow conveyor comprising a laminar body in which an inlet edge, disposed downstream said outlet mouth of said head box, and an outlet edge, disposed immediately upstream the contact line of said flexible belt with said first drum, are provided.
 2. The machine according to claim 1, wherein said laminar body has a shaped surface turned toward said flexible belt in which, starting from said inlet edge, a bent portion with the convexity turned toward said flexible belt is present, followed by a straight portion which ends with said outlet edge.
 3. The machine according to claim 2, wherein said straight portion is parallel disposed with respect to said flexible belt.
 4. The machine according to claim 1, wherein said laminar body is fixed to said conveying conduit of said head box.
 5. The machine according to claim 1, wherein said laminar body is joined to opening adjustment means of said outlet mouth of said conveying conduit.
 6. The machine according to claim 5, wherein said opening adjustment means of said outlet mouth comprise a sliding blade disposed on the width of said conveying conduit and provided on one side with screw means to fix connection means to said laminar body on said conveying conduit and on the opposite side.
 7. The machine according to claim 6, wherein the surface of said sliding blade turned toward the opposite side of said flexible belt is inclined with respect of said flexible belt at an angle having double amplitude with respect to the inclination angle of the corresponding surface of said laminar body, it too turned toward the opposite side of said flexible belt.
 8. The machine according to claim 7, wherein said surface of said laminar body turned toward the opposite side of said flexible belt abuts against a support structure fixed to said conveying means.
 9. The machine according to claim 8, wherein said surface of said laminar body has a substantially intermediate area abutting against said support structure.
 10. The machine according to claim 6, wherein said screw means comprise a plurality of screws, each of them being provided with a control wheel, passing through a corresponding slot obtained in said sliding blade and being screwed in a corresponding threaded hole obtained in said conveying conduit.
 11. The machine according to claim 1, wherein said flow conveyor is provided with side shoulders, applied to said laminar body, to contain said suspension of cellulose fibres.
 12. The machine according to claim 1, wherein it comprises thrust elastic means put in contact with the outer surface of said flexible belt on the opposite side with respect to said laminar body.
 13. The machine according to claim 1, wherein the outer surface of said first cylindrical drum comprises circumferential grooves.
 14. The machine according to claim 1, wherein said collecting means of said liquid and said pollutant agents filtered through said flexible belt consist of a first collecting tank placed below said first drum.
 15. The machine according to claim 14, wherein it further comprises a second collecting tank placed below said second drum.
 16. The machine according to claim 1, wherein said driving means comprise a motor coupled with a kinematic mechanism formed by a first pulley keyed to said motor, a second pulley keyed to said first drum and a transmission belt wound between said pulleys.
 17. The machine according to claim 1, wherein said collecting means of said cellulose fibres comprise at least a scraper, put in contact with the lateral surface of said second drum, and a container for collecting the fibres detached from said scraper, placed under said scraper.
 18. The machine according to claim 17, wherein said collecting container is provided with means for extracting said fibres.
 19. The machine according to claim 18, wherein said means for extracting said fibres consist of an auger.
 20. The machine according to claim 1, wherein said first drum is disposed at a higher level with respect to said second drum.
 21. (canceled) 